Polycrystalline Nd2CoIrO6 double perovskite crystallizes in monoclinic crystal structure with P21/n space group. The average grain size of powder sample is 400-500 nm. The dielectric, impedance and ac conductivity of the sample were studied in the temperature range 5-300 K and in the frequency range 20 Hz-2 MHz. Dielectric constant reveals a step like increase from low temperature value of ∼5 to colossal value of ∼104 at high temperature. High value of dielectric constant is associated with Maxwell-Wagner polarization due to large grain boundary capacitance. Cations (Co2+ and Ir4+) disorder leads to variable range hopping conduction of electrons in grain and grain boundary regions. Distribution of grain size induces distribution of relaxation time as confirmed from depressed semicircles in Nyquist plots. Frequency dependent conductivity follows universal power law behavior.

中文翻译：

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Nd2CoIrO6 双钙钛矿的介电阻抗谱

多晶 Nd2CoIrO6 双钙钛矿结晶为 P21/n 空间群的单斜晶体结构。粉末样品的平均粒度为400-500 nm。在 5-300 K 的温度范围和 20 Hz-2 MHz 的频率范围内研究了样品的介电、阻抗和交流电导率。介电常数显示出从低温值 ~5 到高温值 ~104 的巨大值的阶梯式增加。由于大的晶界电容，高介电常数值与 Maxwell-Wagner 极化相关。阳离子（Co2+ 和 Ir4+）无序导致晶粒和晶界区域中电子的可变范围跳跃传导。奈奎斯特图中的凹陷半圆证实了晶粒尺寸的分布会导致弛豫时间的分布。